Enterovirus 71 (EV71), a major pathogen that is responsible for causing hand-foot-and-mouth disease (HFMD) worldwide, is a member of the Human Enterovirus species A, family Picornaviridae.

Since the late 1990s, a series of large HFMD epidemics caused by EV71 have been reported in the Asia-Pacific region. Notably, there is evidence that the most severe cases from these epidemic outbreaks are associated with neurological disorders with CNS involvement caused by EV71 infection. Because of these EV71 infection-related public health issues, the research and development of EV71 vaccine candidates have been heavily promoted.

Recently, several EV71 vaccine candidates have been evaluated in animals but no final results of clinical trials, including inactivated vaccine, attenuated vaccine, subunit vaccine, DNA vaccine, epitope peptide vaccine, virus-like particles (VLPs).

Basing on the previous studies of elicited protection in mice and rhesus monkeys, a formalin-inactivated EV71 vaccine (Human Diploid cell, KMB-17 Cell) has been licensed by SFDA in China, Dec. 2010. The phase I clinical trial was completed, during four months, in Guangxi Province, China. The phase II clinical trial has been carried out, from July 2011. The purpose of phase II is to evaluate the safety and efficacy of the formalin-inactivated EV71 vaccine in Chinese infants (from 6 to 36 months old).

Hand-foot-and-mouth disease (HFMD) is a significant cause of death, usually characterized by vesicular lesions on the skin and oral mucosa and high morbidity rates in children. Additionally, occasional fatal cases have been reported involving brainstem encephalitis and myelitis associated with cardiopulmonary collapse. Pulmonary edema/hemorrhage and respiratory failure are the major causes of death among children less than five years old.

Enterovirus 71 (EV71), a major pathogen that is responsible for causing HFMD worldwide, is a member of the Human Enterovirus species A, family Picornaviridae. Since the late 1990s, a series of large HFMD epidemics caused by EV71 have been reported in the Asia-Pacific region. Notably, there is evidence that the most severe cases from these epidemic outbreaks are associated with neurological disorders with CNS involvement caused by EV71 infection. Because of these EV71 infection-related public health issues, the research and development of EV71 vaccine candidates have been heavily promoted.

Recently, several EV71 vaccine candidates have been evaluated in animals but no final results of clinical trials, including heat-inactivated or formalin-inactivated vaccine, live-attenuated vaccine, recombinant viral protein 1 (VP1) vaccine, VP1 DNA vaccine, VP1 epitope peptide vaccine, EV71 virus-like particles (VLPs) and bacterial or viral vector expressing VP1. Overall, the inactivated whole-virus vaccines seem to be more immunogenic than recombinant VP1 and DNA vaccines.

Basing on the previous studies of elicited protection in mice and rhesus monkeys (Ying Zhang, et al. Pathogenesis study of Enterovirus 71 Infection in Rhesus Monkeys. Lab Invest, 2011, doi:10.1038/labinest.2011.82; Longding Liu, et al. Neonatal Rhesus Monkey is a Potential Animal Model for Studying Pathogenesis of EV71 Infection. Virology, 2011, 412:91-100; Chenghong Dong, et al. Immunoprotection Elicited by an Enterovirus Type 71 Experimental Inactivated Vaccine in Mice and Rhesus Monkeys. Vaccine, 2011, doi: 10.1016/j.vaccine.2011.06.044.), a formalin-inactivated EV71 vaccine (Human Diploid cell, KMB-17 Cell) has been licensed by SFDA in China, Dec. 2010. The phase I clinical trial was completed, during four months, in Guangxi Province, China.

The results showed that the formalin-inactivated EV71 vaccine (Human Diploid cell, KMB-17 Cell) was safety in Chinese adults (from 18 to 49 years old), children (from 3 to 11 years old) and infants (from 6 to 35 months old). This vaccine could induce specific cellular and humoral immune responses.

The phase II clinical trial has been carried out, from July 2011. The purpose of phase II is to evaluate the safety and efficacy of the formalin-inactivated EV71 vaccine in Chinese infants (from 6 to 36 months old).

Inclusion Criteria:

• Healthy subjects (6-35 months infants) as established by medical history and clinical examination
• Full-term (37-42 weeks), weight ≥ 2500 g when it was born
• The subjects' legal guardian must be aware of this vaccines
• The subjects' legal guardian voluntarily participate in the study and signed Informed Consent Form
• Subjects with temperature ≤ 37.0℃
• The subjects' legal guardian with the ability and objective to comply with the requirements of the protocol
• Persist for a 2-month visit and receive blood tests according to program requirements

Exclusion Criteria:

• Subject who has a clinical diagnosis history of Hand, Foot and Mouth Disease (HFMD)

  • 37 weeks gestation

• weight ≤ 2500 g when it was born

• Allergy or serious side-effects to a vaccine or any ingredient of vaccine

• Epilepsy, seizures, convulsions, neurological illness

• Congenital or hereditary immunodeficiency

• Autoimmune disease

• Severe malnutrition or dysgenopathy

• Asthma, thyroidectomy, angioneurotic edema, diabetes or cancer

• Asplenia, functional asplenia, and any circumstances leading to the asplenia or splenectomy

• Clinical diagnosis of coagulopathy (such as clotting factor deficiency, coagulation disorders, platelet abnormalities), significant bruising or blood clotting disorder

• Acute illness or acute exacerbation of chronic disease in last 7 days

• Any prior administration of immunodepressant or corticosteroids in last 6 months

• Any prior administration of blood products in last 3 months

• Any prior administration of live-attenuated vaccine in last 28 days or 1 months

• Any prior administration of subunit or inactivated vaccines in last 14 days Under the anti-TB prevention or therapy

• Fever before vaccination, axillary temperature ﹥37.0℃

• The laboratory test abnormalities before vaccination, including blood tests (hemoglobin, total white blood cells, WBC, platelets), blood biochemistry tests (ALT, total bilirubin, direct bilirubin, Cr, BUN) and urine tests (urine protein, urine sugar, blood cells), etc.

• Hypertension or hypotension. Systolic blood pressure ﹥140mmHg and/or diastolic blood pressure ﹥90mmHg; systolic blood pressure ﹤90mmHg and/or diastolic blood pressure ﹤60mmHg

• Any condition that in the opinion of the investigator, may interfere with the evaluation of study objectives